Magnetic pickup arm biasing device



Jan. 30, 1951 J, o K E 2,539,784

MAGNETIC PICKUPHARM BIASING DEVICE Filed May 20, 1944 2 Sheets-Sheet 1 E0 o o o 0 6I o65,8

LECTRIC MOTOR naive-N runn- ABLE TURN-TABLE MOTOR swn'cu FOR "I" CONTROLOF Y POWER JUPPLK Z 21 6'6" -m|u| A INVENTOR. dlacmso/v OJQEBER.

M,MM

ATTORNEYS.

MAGNETIC PICKUi ARM BIASING DEVICE mill" f 65 v r 20 A In r I 4INVENTOR. \J 4YCKJON O. MEBEE.

M ,CauJa-fl 4w! ATTORNEYS.

Patented Jan. 30, 1951 UNITED STATES PATENT OFFICE 2,59,7s4 MAGNETICPICKUP ARM BIASING DEVICE JaksoriO. Kleber, Loiig Island City, N.- Y;Application May 20, 1944, Serial No; $3 6,454

This invention relates to improved phonographs, certain features thereofbeing such as to particularly adapt the construction for use by theblind. The construction is also well adapted for portable use by membersof the public generally while traveling on boats, ships or vehicles,without danger that the sound records or the mechanism will becomeinjured or inoperative due to the motions of the conveyance. Theconstruction, furthermore, includes various features making possibleimproved sound reproduction when using inexpensive or worn records, andrecords of such inferior quality or having such fine grooving that sameare not capable of being played on phonographs heretofore generallyavailable. The invention also involves certain features for insuringproper operation of the mechanism by careless or unskilled persons,without danger of injury of the parts.

According to one important phase of the invention, the stylus-carryingassembly is arranged to include a magnet, either a strong permanentmagnet or an electromagnet of adjustable strength, arranged with itspole or poles so positioned as to apply attractive force during. theplaying of the record, in a direction tending to hold the needle orstylus down in position in the sound track. For example, if themagnet isat or adjacent the sound-translating device, or forms a part of 'amagnetic pick-up, then the magnet poles are positioned so as to be infairly closely spaced relation to the turntable, the latter being formedof a suitable magnetic metal such as steel. Thus, as thesound-translating device moves across the record, succeeding portions ofthe turntable form a substantial part of the magnetic circuit of themagnet and the consequent at! tractive force causes the stylus in effectto cling in the sound track to a surprisingly effective den gree, eventhough the machine may betilted to a high angle or even though the soundtrack may be so fine, seriously worn or poorly made that the recordcould not be played at all with the usual phono raph. At the same timethe. magnet-1c attractive force is such that, particularly with recordswhich are old or poorly made, the. quality of the sound reproduction is,improved as compared with what could otherwise be accomplished, in thatnoises and sounds due to extraneous vibrations, etc., are minimized. If.de-

sired, the magnet which is fixed on the styluscarrying assembly may bein a position to apply attractive force during the playing of therecord, to a magnetic element other than the record. carrier, forexample a bar of iron. fixed to. the.

2 casing and extending along the path of travei of the magnet. Suchmagnet maybe an electrm magnet, adjustable if desired, by varying itscurrent or position.

Various further and more specific objects, features and advantages ofthe invention will appear from the description given below takeninconnection with the accompanying drawings illustrating byway ofexample a preferred form of the invention. The invention consists insuch novel features and combinations as may be shown and described inconnection with the apparatus herein disclosed.

In the drawings:

Fig. '1 isa plan View showingvarious features of a preferred form of theinvention;

Fig. 2 is a side elevational view of the same, the casing parts beingshown in section.

Fig. 3 is an elevational view of the tone arm,

portions adjacent theaxis thereof being shown in section Fig. 4. is anenlarged vertical sectional view.

of the pick-up device assembly substantial-lyalong line 55 of Fig. 6;

Fig. 6 is a sectional view taken substantially along line 66 of Fig. 5;and

Fig. '7 is a perspective view showing portions of the pick-up" deviceinseparated condition.

Referring to Fig. 1,;the phonograph as here shown is adapted to becontained in a cabinet as at [0, which may also contain. suitable vacuumtube amplifying equipment if desired. The cab. inet may be provided witha hinged cover it, which may contain if desired an electrically ac.-tuated loud speaker (not shown).

A turntable l2 may be provided and driven in; the usual way, as by anelectric motor or spring motor. The turntable is preierably-formed as a.disc of steel or other suitable; ferromagnetic metal over which a mat,of softrubber B may besecured as by a suitable adhesive. Records as at Hof the various known disc types are adapted to be carried upon thisrubber mat and held in place by the usual center pin l5- As best shownin Fig. 3,. the stylus-carrying. arm; assembly H. may comprise; a castmetal body member I8 formedintegral'ly with ashaft l9; for. pivotalmounting of same to turn about a. vertical axis to permit the stylus totravel across the record being played; and permitting the arm. as.-

sembly to be placed alongside the record when inactive. The shaft I9 maybe carried in a bearing member 20 fixed to a base 2i within the cabinetso that the bearing portion extends down through the base and may besecured as by a nut 22. The shaft portion H] at its lower end may alsobe removably secured as by a nut 23. One side of the member [8 may beformed to include an integral counterweight portion 24 diametricallyopposite an arm portion 25. Within the outer end of the arm 25 a pin 26is fixed in position as by a set screw 21. This pin forms a horizontalpivotal supporting axis for the pick-up assembly which may include aninverted channelshaped metal piece 28 pivoted on shaft 26, and removablysecured to an arm member 29 as by screws 3h. The arm member 29 may beformed of highly transparent insulation material such as a methylmethacrylate product, and may be provided at the upper side of its outerend with a finger piece portion 3! of the same material. A magneticfpick-up type of sound-translating device is, indicated at 32 secured tothe under side of the outer portion of arm 29 as by screws 33 (Fig. Asshown in Fig. 4, the outer end of arm 29 may be formed with aninternally depending pointer portion 3a which is also transparent. Asmall electric lamp as at 35 (Figs. 1, 3) may be mounted within anydesired portion of the arm 29 so as to direct light along this arm toilluminate same, as well as illuminating the finger piece 3 I orindicating its outline, and also internally illuminating the pointerpiece 34. The pointer piece will thus serve as a guide to the operatorfor indieating the location at which the pick-up device should be placedin order to have the stylus which is concealed on its under side,properly enter the initial portions of the sound track on the record.This means of illuminating the arm, finger piece and pointer, enablespeople who may be nearly blind to more readily operate the machine, andalsogreatly facilitates operation of the machine by anyonenot blind, inthe dark or under conditions of poor illumination, without the necessityof flooding the machine as a whole with bright light.

As-shown in Figs. 5-7, the pick-up device may 'be contained within asmall housing of non-magnetic sheet material as at 36, and may includean angular frame piece of non-magnetic metal 31, in an upper plate-likeportion in which the screws 33 are secured. As shown in Fig. 7, themember 31 has a depending portion 38 within the back side'of which acavity may be formed for receiving a suitable shunt resistance device 39for the pick-up coil, hereinafter referred to. That is, the device 38may comprise layers of insulation between. which a suitable resistanceelement 3Q may be clamped (Fig. 6). As shown in Figs. 5 and 6, the lowerpart of member 3'! may comprise a forwardly extending integral bracketportion 40 to which a pair of magnet pole pieces 4!, 42 may be securedas by screws 43.

The pole pieces 4I,,42 as best shown in the under side view thereof inFig. 6, may be formed with tapered portions directed toward each otherto concentrate the flux at a narrow gap 44. A magnetized bar of highlymagnetic metal 45 may be slidably and removably received with its undersurface resting upon the upper surfaces of pole pieces ll, 42, the uppersurface of the bar contacting the under surface of the upper plate-likeportion of the member 31,

The stylus or needle may take the forin of a sapphire 46 fixed toprotrude down from the lower edge of a small armature member 57 formedof metallic metal. This armature member may for example comprise a tinyrectangular piece of sheet metal mounted in a vertical plane and thelower edges of which is slotted centrally to receive the sapphire andthe upper edge of which is soldered to a phosphor bronze strip 48. Thisstrip may have an inverted V-shaped cross section and has its endssecured to posts as at 49, 55] which depend integrally from bracketportion M8. The member 248 for example may be secured to the lower endsof these posts as by clamping screws 5| threaded to receive at theirlower ends small clamping blocks as at 52. Preferably, member 48 shouldalso have its ends soldered in position While same is subject tolongitudinal tension.

The pick-up coil may be spirally wound in the form of a small disc 53received and retained within slots therefor formed in the facingportions of the two pole pieces 4|, 42. Suitable connections from thiscoil with the resistance 39 shunted across same, may extend as shown at54 (Fig. 3) back along the arm and down through the hollow shaft I 9 toamplifier and loud speaker equipment of any desired type.

It is noted that the lower surfaces of the pole pieces 4! and 42 arearranged in closel spaced parallel relationship with the upper surfaceof the record disc I4. By selecting the record-supporting mat E3 ofappropriate thickness, the air gap between the pole pieces and therecord support l2 of magnetic material, may be so chosen that aneffective attractive force is maintained by the magnetic field tendingto cause the stylus to cling within the sound track of the recorddespite irregularities in the track or the occurrence of forces whichwould ordinarily cause the stylus to jump out of the track. Also withthe parts arranged as shown, by making use of this magnetic attraction,it has been found possible to obtain excellent results in playingrecords in which the sound track is very finely embossed, for instancewith as many as 280 lines per inch, and it was found that the sapphirewould not escape from the track even when the machine is tilted toangles as high as These advantages of the invention are particularlydesirable if the machine is to be used by the blind since, for reasonsof economy, they may have occasion to use inexpensive records for longperiods after same have become worn; also, since these advantages makeit possible for the blind to readily use a machine when traveling, attimes when no other activities would be open to them.

It should be noted that the effect of the magnetic attraction inretaining the pick-up device in position is in various respects quitedifferent from the effects which would be accomplished by increasing theweight of the pick-up. That is, of course, any added weight tends toincrease the inertia, thereby tending to detract from the quality of thereproduction, and in case the machine is abruptly moved or jolted, orthe sound track is irregular, any such increased inertia effects due toadded weight will tend to cause the stylus to bounce or fly out of thetrack, unless the weight applied is excessive. It will be apparent thatby improving the tracking with the aid of magnetic attraction, thedisadvantages of using added weight for the purpose are avoided. Themagnetic attraction as here used is also to be distinguished from theeffects of using a spring for the purpose as has heretofore beenproposed. The use of a spring involves mechanical difficulties in sopositioning and attaching same that Varying frictional effects will-beavoided, while leaving the pick-up arm free for easy manipulafition andproperpropulsion by the stylus.

It should be noted thatwith magnetic attraction used as above described,the attractiveforce is largely in a downward direction toward therecord, sidewise movements of the pick-up device being only slightlyrestrained magnetically. Accordingly, in order to obtain the bestresults with the invention, particularly on portable machines subjecttofabrupt movements during use, the stylus-carryingarm assembly shouldbe substantially balanced'against any tendency for an gular-movementabout the axis of shaft l9 when the machine is tilted in any direction.Such balancing'ma'y be accomplished as best shown in Fig. l, in thefollowing way. If we draw a line as at'athrough the axis of shaft I 9and 'in-a'position Such that the weight of counterweight 24 is equallydistributed at the two sides of such line, then'the weight of thepicl'-up and supporting arm structure therefor should'also beequallydistributed at the two sides of such line. Also, if we drawanother line b perpendicular to line a, through the axis of shaft l9,the parts at each side of this line should 'beso arranged, as toposition' and weight, that when the axis-is tilted, gravity will causeequal moments of force respectively, due to the parts at each side ofline b. It is noted that the counterweight 24 is effectiveessentially-in normally horizontal directions as distlnguished fromcounterweights heretofore used on various phonographtone arms in amanner such as to act in vertical directions about a normally horizontalaxis.

As shown in Fig. 4, when the machine is not in use, the pick-up armassembly may beturned to inactive position so that the pick-up device 32will be supported by a rest piece 55. This may comprise a somewhatresilient piece of sheet metal bent to the shape shown in Fig. 4 andattached to the base 2 I, andhaving an upstanding stop portion 56. Thispiece may also be formed with a depressed area 51for receiving thestylus or sapphire while the bottom of the pick-up casing rests upon theremaining areas. The piece 55 may be formedpreferably-of magneticmaterial accompanied if desired by a thicker pieceo'f magnetic material58 on its under side, whereby a strong attractive'force will occur forholding the pick-up in position on therest piece and at the same timethe magnetic rest piece may be arranged to act as a keeper forthe-magnet.

As shown in Figs. 1-3, a switch 60 may be provided to control thecircuit of the turntable motor. This switch may be of a "suitableknowntype such as now commercially available under the name microswitch forexample, having an operating button as at 6| positioned in the path ofthe lower surface of the counterweight 2'4. The button BI is preferablyso positioned that when the pick-up arm assembly is at any position withthe stylus outside the circumference of the outer sound track on therecord, then the button Bl will be depressed for disconnecting themotor. Thus whenever the pick-up arm after playing a record, is moved toinactive position, the motor and turntable will be stopped. Then afterthe record has been replaced, the operator without the aid of sight, cangrasp the pickup and move it over to the edge of the turntable withassurance that the turntable will be stationary and thus readily graspedwith the hand to facilitate bringing the stylus into proper positionbefore the turntable starts, and thus avoiding the danger of jamming thestylus against theturntable when rotating. The above described magneticfeatures for holdinga stylus in place with're'spect to a rec'-ord,"mayalso be useful in recording operations when performed by theblind. Thatis, a slight degree of magnetic attraction betweentherecording stylus andth'e record may be used to prevent unintendeddisplacement of the stylus by the-blind person while a record is beingout. Also it will be understood that the turntable motor control featureas correlated with the-position of the stylus-carrying arm, is welladapted for use by the blind in recording apparatus.

As shown in Figs. 1 and 2, the casin cover Il may be accompaniedby bracemeans comprising two hinged parts as'at 62, 63 ofa.-wellknown'construction, for holding the cover in thedesired openposition when the, machine is be ing used. To prevent injury ofthepick-up parts, particularly on a portable machine,- it'is of courseimportant for the pick-up assembly to be placed in inactive position onthe rest piece before the cover is closed. According to the presentinvention, means are provided to lock or stop the cover-supportingmembers 62, 63 against closing of the cover until the pick-up assemblyis placed on the rest piece. This maybe accomplished by forming thecounterweight 24 with an upstanding arcuate cam surface 64 adapted toengage an arcuately shaped lever member 65 carried by a rockable support66 pivoted to the base at 67. The support. 66 may comprise a U-shapedpiece of sheet metal, to one branch 68 of which the lever 65'i'sconnected. and the other branch 69 comprising the stopping post adaptedto be swung into position under the lower end' of member 63 as shown inFig. 2, whenever the pick-up arm assembly is moved from its position onthe rest piece. The support 66 may be normally biased tobring the post69 into locking position as by a spring 66 having one end se cured tothe base 2| and its other end pressing against the post 69. Thus,whenever a record is being played or when the pick-up is being moved toor from' its rest position, the cover will be locked against closing.For blind persons this feature is of course particularly advantageous. I

In order to insure that the turntable motor circuit, lampcircuit andamplifier circuits, etc., will be disconnected when the cover iscIosed,a switch 10 may be mounted in the cover as shown in Fig. 2, having anoperating spring '1 I adapted to engage the upper surface of thecounterweight 2 4 when the cover is closed, and, provided thecounterweight is in a position with the pick-up located on the restpiece. The: switch 10 may be of the same construction as; theabovementioned switch except for the added sprin H. This switch may besuitably connected so as to cut off the power to all of the electricaldevices in the machine. But it will be particularly noted that this willonly occur if the pick-up is in inactive position. Thus even if theautomatic cover locking means should for any reason become defective ornot be used, so that the cover is free to be closed. with the pick-upnot on the rest piece, then that fact will be evident to a blind personupon closing the cover, since the current to the amplifier and loudspeaker will still be on and he will be able to hear the resultingslight hum.

While the invention has been described in detail with respect to aparticular preferred examassays-i pie, it will be understood by thoseskilled in the art after understanding the invention, that variouschanges and further modifications may be made without departing from thespirit and scope of the invention, and it is intended therefore in theappended claims to cover all such changes and modifications.

What is claimed as new and desired to be secured by Letters Patent is:

1. In a phonograph, the combination of a rotatable record supportcomprising magnetic material substantially coextensive at least with theareas of the record which include the sound track, stylus-carryingmeans, a support structure for such stylus-carrying means for supportingsame in position for stylus engagement with the sound track, saidstylus-carrying means being propellable across such record areas bystylus engagement with the sound track, and a magnet carried by saidmeans in a position whereby successive magnetic portions of said recordsupport form an effective part of the magnetic circuit of the magnet andthereby causing said carrying meansduring its travel across said recordareas to be urged toward the support, for preventing escape or" thestylus from the sound track.

2. In a phonograph, a record support comprising magnetic material, incombination with a magnetic pick-up device, a support structure forholding said magnetic pick-up device in close proximity to said recordsupport, the magnet of said pick-upf being thus positioned to applyattractive force between said device and said support during playing ofthe record.

3. In a phonograph, a record support comprising magnetic material forsupporting a record having a groove wave sound track, stylus-carryingmeans mounted to travel across a record on such support, and a magnetcarried by and rigidly associated with said means in a position to exerta substantially attractive force on said support for preventing escapeof the stylus .from the groove sound track of the record.

4. In a phonograph, a magnetic pick-up including a stylus-carrying meansmounted to travel over a rotatable record, a magnet comprising a part,of said magnetic pick-up and mounted to travel with said means, saidmagnet providing a. magnetic field for the operation of said magneticpick-up, magnetic means extending along beneath the path of such travel,the magnet having a pole or poles positioned to apply substantiallyattractive force between said carrying means and the latter means, and arest piece of magnetic material for said carrying means when inactive,said magnet being positioned to then come into close proximity with saidrest piece whereby said carrying means is held in inactive position bymagnetic attraction.

5. In a phonograph, a stylus-carrying arm assembly pivotally mounted toSWing about a fixed normally vertical axis, said assembly including 9.

body member having an integral counterweight on one side of said axisand an arm on the other side thereof, said arm being pivotally connectedto said body member to swing about a normally horizontal axis, the partsof said assembly being substantially balanced against angular movementof the assembly about said axis upon tilting of the phonograph, a magnetmounted to travel with said assembly, magnetic means'extending alongbeneath the path of such travel, the magnet having a pole or polespositioned to apply substantial attractive force between thestyluscarrying means and said magnetic means dur ing the'playing of arecord, for preventing escape of the stylus from the sound track of therecord.

'6. In a phonograph, the combination of a rotatable record supportcomprising magnetic material substantially coextensive at least with theareas of a record which include the sound track therefor,stylus-carrying means, a'support structure for said stylus-carryingmeans for holding same in position for stylus engagement with the soundtrack, said stylus-carryin means being propellable across such recordareas by stylus engagement with the sound track, and a bi-polar magnetcarried by said means, the poles being on opposite sides of the stylusand in a position whereby successive magnetic portions of said recordsupport from an effective part of the magnetic circuit of the magnet andthereby causing said stylus-carrying means during its travel across saidrecord areas to be urged toward the support, for preventing escape ofthe stylus from the sound track.

7. In a phonograph, a record support comprising magnetic material,stylus-carryin means mounted to travel across the record on suchsupport, and a bi-polar magnet carried by said means, the poles thereofbeing disposed on opposite sides of the stylus and in a position toexert a substantially attractive force on said support for preventingescape of the stylus from the sound track of the record. JACKSON 0.KLEBER.

REFERENCES CITED Number

